This invention relates to the splicing together of ends of a pair of optical fibers using an intense beam of laser radiation.
There has been heavy growth in the area of optoelectronics and particularly in the utilization of optical fibers as the preferred medium for carrying heavy communication loads over long distances and safely past strong sources of electronic interference. Such optical fibers have low-loss capabilities, the optical transmission path providing electrical input and output isolation in a light weight and low cost cable, while avoiding susceptibility to electromagnetic induction effects.
An optical fiber comprises a first transparent dielectric cylinder surrounded by a second transparent dielectric cylinder, light transported by a series of reflections from wall to wall off an interface between the inner cylinder (the core) and the outer cylinder (the cladding). The reflections are made possible by a high refractive index of the core material and a lower refractive index of the cladding material, such that light is transported from a light source to a light detector. These cylinders are typically covered by a protective plastic jacket and there may also be included strengthening members which surround and further protect the optical fiber. Multiple optical fiber cables are also used.
Provision must be made for joining optical fiber cables together as joints are frequently employed in long haul fiber links as well as in local area networks (LAN) to form a permanent joint between fibers in the field. However, coupling optical fibers can result in various losses such as through misalignment of the fiber ends, gap losses, etc.
Proper joining, preferably by splicing of the ends, is imperative to achieving high performance from an optical fiber link. Such fiber splicing is currently performed by arc-fusion or mechanical splicing techniques. In arc-fusion splicing, an electric arc is employed to provide localized heating at the interface between two butted, pre-aligned fiber ends causing them to soften and fuse. In mechanical splicing, fibers are held in alignment by some mechanical means (such as special tubes, grooves, etc.) and optical epoxies are injected at the fiber joint to splice the fibers. However, current splicing methods often restrict the quality of the joint and thus can degrade the transmitted signal. For example, the use of arcing electrodes may cause contamination of the joint. Further, the time required to obtain a joint is excessive.
Although lasers are extensively used in many applications such as welding, soldering, marking, etc., their potential for splicing optical fibers has not been exploited. This is partly due to the difficulty in determining the appropriate parameters for laser splicing and partly because of problems with process implementation due to small fiber size (diameter of about 100 microns), complicated further because the fiber is itself transparent to light and absorption of laser light into the fiber is very small. As such, melting of the fiber ends may not occur easily and if some melting does occur, it is difficult to assure uniformity. Consequently, successful commercial laser splicing of optical fibers has not been achieved.
It is an object of the present invention to provide a method for fusing optical fiber ends rapidly and with low distortion.
It is a further object to provide a method for fusing optical fiber ends with a precise heat source to minimize defects.
It is another object to provide a method for fusing optical fiber ends that is rapid, easy to use and adaptable for use in remote field locations with low power consumption.
It is yet another object to provide a field usable apparatus for fusing optical fiber ends using a laser as the heat source.
It is another object to provide a method and apparatus for the rapid epoxy fusing of the ends of a pair of optical fibers.
These and other objects of the invention are achieved by a method for fusing the ends of a pair of optical fibers together comprising:
providing two optical fiber ends, placing the two optical fiber ends in coaxial alignment, such that the ends are in contact and applying an intense beam of electromagnetic radiation to the contacted ends in an amount sufficient to effect melting and fusing of the fiber ends.
In one embodiment of the invention, the beam of electromagnetic radiation is a laser beam that is of sufficient intensity so as to create a plasma effect during fusing.
According to conventional thinking, light dissipation at the point of irradiation should result in erratic performance, distortion and/or higher attenuation. It has been discovered that a laser operating at specified parameters can achieve a plasma effect which results in high energy absorption, resulting in an excellent fiber joint, with low power consumption.
The apparatus of the invention comprises means for coaxially aligning two optical fiber ends, means for generating an intense beam of electromagnetic radiation and means for applying the intense beam of electromagnetic radiation to the aligned fiber ends for a time sufficient to effect fusing of the fiber ends.
Preferably, the apparatus further includes means for observing the fiber ends, means for testing the fused ends to assure optimum performance, and control means for controlling the fusion process.
Most preferably, a computer controlled laser system using laser diodes, a micro positioning system and a CCD camera are used to obtain high quality remote field location optical fiber splices, the system optimally being battery powered.
In another embodiment of the invention, the apparatus includes means for applying a curable joining compound to the fiber ends and access means for applying the beam of electromagnetic radiation to the fiber ends and joining compound to advance the curing process.